The present invention relates to high-lift arrangements for a blade of a motor grader. In particular, the invention relates to an improved method of supporting the blade beneath the frame of a grader.
In the past a number of arrangements have been proposed for supporting the blade of a motor grader and in general these can be broken into two groups. The first group uses a beam extending either side of the frame of the motor grader and pivotable about the frame, and the second group uses separate arms, one to either side of the frame, and in many cases these arms are movable to various positions. There has also been a number of arrangements where either the beam or the arms are fixed in position on the grader frame. The fixed position arrangements are generally limited with respect to the extent and position, either side of the grader, that the blade can be positioned. In general, the most demanding specification requires that the grader blade be capable of moving to either side of the mainframe of the grader from a perpendicular position at one side to a perpendicular position at the other. The fixed arm or fixed beam arrangement have limited adjustability, however in many applications the extreme positions of the blade will not be used. The blade support arrangement should be adjustable to effect 2 to 1 and 1 to 1 banking either side of the grader as well as a ditching orientation either side of the grader.
In addition to the very demanding specifications set forth above which have generally been met with either the pivoted beam or the movable arms, the support arrangement for the motor grader blade should be convenient to use and adjust between the various positions. The system should be such that there is not any substantial fouling problems with respect to the movement of the cylinders to achieve the various positions, as fouling problems can lead to extensive damage of the hydraulic components and other structural components. Furthermore, the support arrangement for the blade of the motor grader must take into account the visibility of the operator from the cab and certain specific points of the blade which are considered somewhat critical. For bank grading, it is generally noted that the heel of the blade should be positioned outside of the wheels so that the wheels do not contact the graded surface and, therefore, the heel of the blade should be visible for this particular operation. Furthermore, the toe of the blade should be visible as this is the other extreme position that is being graded.
The ideal blade positions include the 90.degree. high-lift to either side of the grader, a position of the blade which is approximately 63.degree. to effect a 2 to 1 banking operation, and a further banking position of the blade at about 45.degree.. The 45.degree. position and the 63.degree. position are generally considered the most frequent positions of the grader blade and the positions which a system must satisfy. Therefore, the flexibility of the system and the ease of adjusting the same should be evaluated with respect to these normal positions, although some merit must be accorded the 90.degree. position as well as the horizontal beam position.
Our earlier patent, U.S. Pat. No. 4,340,119 uses a beam centrally pivoted atop the grader frame with a locking arrangement generally provided beneath the frame. This arrangement generally satisfies the standards set forth above, however the locking arrangement beneath the frame, which is a mechanical arrangement, reduces the clearance beneath the frame and requires a fair degree of accuracy with respect to the locking position of the beam when the beam position is adjusted. The advantages of this mechanical lock are the steel to steel locking contact which is the generally accepted standard in the industry.
The structure previously referred to above, having movable arms either side of the grader frame, again uses a pin-type lock arrangement for fixing the arms at various positions relative to the frame and often these pins are either mechanically movable to allow adjustment of the arms or beam or are hydraulically actuated to effect adjustment of the components. However, the fixing of these components in a predetermined position on the frame is achieved by a mechanical type lock. The problem of accurate positioning for locking is compounded in the movable arm system in that two arms must be locked rather than a single beam and freezing of locks occurs making the arms difficult to release.